The wave transformation model STWAVE was applied to calculate wave heights and directions at the entrance to Willapa Bay. The model was driven with input waves from an offshore buoy and compared to nearshore pressure gauge measurements. Including current in the bottom pressure gauge analysis for Willapa had a significant impact on wave height estimates (neglecting current resulted in up to 20% overestimates of wave height during flood current). Verification results showed reasonable agreement between calculations and measurements (root-mean-square (RMS) errors in wave height of 0.1–0.3 m and RMS errors in direction of 7–15 deg). The dominant transformation process for waves in the bay was wave breaking over the Willapa bar. The dissipation is controlled by the tide elevation over the bar. Wave-current interaction is significant only in the outer Willapa entrance channel where currents reached 2 m/sec. Wave heights on ebb increased up to 80 percent and on flood decreased up to 20 percent.